From: Madhavan Srinivasan <maddy@linux.vnet.ibm.com>
To: Michael Ellerman <mpe@ellerman.id.au>,
Ravi Bangoria <ravi.bangoria@linux.vnet.ibm.com>,
linuxppc-dev@lists.ozlabs.org
Cc: benh@kernel.crashing.org, paulus@samba.org, tglx@linutronix.de,
mingo@kernel.org, kan.liang@intel.com,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] powerpc/sysrq: Fix oops whem ppmu is not registered
Date: Tue, 19 Sep 2017 15:34:40 +0530 [thread overview]
Message-ID: <6d061729-f2a2-ed05-2008-46c78ef4bd6f@linux.vnet.ibm.com> (raw)
In-Reply-To: <87wp4vknxq.fsf@concordia.ellerman.id.au>
On Tuesday 19 September 2017 03:30 PM, Michael Ellerman wrote:
> Ravi Bangoria <ravi.bangoria@linux.vnet.ibm.com> writes:
>
>> Kernel crashes if power pmu is not registered and user tries to dump
>> regs with 'echo p > /proc/sysrq-trigger'. Sample log:
>>
>> Unable to handle kernel paging request for data at address 0x00000008
>> Faulting instruction address: 0xc0000000000d52f0
>>
>> NIP [c0000000000d52f0] perf_event_print_debug+0x10/0x230
>> LR [c00000000058a938] sysrq_handle_showregs+0x38/0x50
>> Call Trace:
>> printk+0x38/0x4c (unreliable)
>> __handle_sysrq+0xe4/0x270
>> write_sysrq_trigger+0x64/0x80
>> proc_reg_write+0x80/0xd0
>> __vfs_write+0x40/0x200
>> vfs_write+0xc8/0x240
>> SyS_write+0x60/0x110
>> system_call+0x58/0x6c
> Thanks.
>
> I added:
>
> Fixes: 5f6d0380c640 ("powerpc/perf: Define perf_event_print_debug() to print PMU register values")
>
> But I don't think I'll Cc stable, I can't think why we'd ever *not* have
> a ppmu registered. How did you hit it?
mpe,
We hit this in a compact mode setup where the distro kernel did not have
the
pmu support for the base pvr.
Maddy
> cheers
>
next prev parent reply other threads:[~2017-09-19 10:04 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-09-19 6:17 [PATCH] powerpc/sysrq: Fix oops whem ppmu is not registered Ravi Bangoria
2017-09-19 10:00 ` Michael Ellerman
2017-09-19 10:04 ` Madhavan Srinivasan [this message]
2017-09-21 1:46 ` Michael Ellerman
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